UNIVERSITY   OF   CALIFORNIA 

COLLEGE    OF    AGRICULTURE 
AGRICULTURAL   EXPERIMENT  STATION 

CIRCULAR  No.  248 
June,  1922 

SOME  COMMON  ERRORS  IN  VINE  PRUNING  AND  THEIR 

REMEDIES 

By  FEEDEEIC  T.  BIOLETTI 


Pruning  cannot  be  reduced  to  a  few  mechanical  rules.  There  is 
no  simple  answer,  that  is  not  misleading,  to  such  questions  as:  How 
should  you  prune  a  two  year  old  vine  ?  or,  How  many  spurs  should  be 
left  on  a  six  year  old  Muscat  ? 

It  would  be  almost  impossible  to  find  two  vines  that  should  be 
pruned  absolutely  alike.  Each  vine  is  a  special  case.  To  watch  an 
expert  prune  one  vine  will  not  aid  a  beginner  to  prune  another  unless 
the  reasons  for  the  cuts  are  explained  and  understood. 

These  reasons,  however,  are  based  on  a  few  relatively  simple  prin- 
ciples. If  these  principles  are  known,  a  good  method  can  be  devised 
and  most  serious  errors  avoided.     Some  of  these  principles  are : 

1.  Each  year  the  vine  bears  a  crop  and  develops  the  buds  which 

produce  the  crop  and  growth  of  the  following  year. 

2.  The  condition  of  a  vine  at  the  end  of  a  year  determines  how 

much  crop  it  can  bear  and  how  much  growth  it  can  make 
the  next  year. 

3.  The  more  crop  a  vine  bears  in  one  year  the  less  growth  it  can 

make  in  the  same  year,  and  vice  versa. 

The  last  statement  indicates  that  growth  and  bearing  vary 
inversely,  but  this  is  true  only  roughly,  and  within  somewhat  narrow 
limits.  If  the  crop  is  reduced  to  zero  we  get  maximum  growth,  but 
if  we  reduce  the  growth  to  zero,  the  crop  disappears  also. 

Neither  of  these  extremes  can  be  reached  by  winter  pruning,  but 
they  can  be  approached  closely.  If  we  prune  off  most  of  the  fruit 
buds  the  vine  will  yield  little  crop  and  will  make  a  vigorous  growth. 
This  can  be  carried  on  indefinitely  if  the  patience  and  the  bank 
account  of  the  grower  hold  out.  If  we  leave  most  of  the  fruit  buds, 
the  vine  will  try  to  produce  a  very  large  crop  and  may  even  succeed 
for  one  year.  During  this  year  the  growth  will  be  small  and  if  Prin- 
ciple 2  above  is  true,  it  will  have  little  crop  or  growth  the  next  year. 
Repetition  of  this  attempt  the  second  and  the  third  year  may  result 
in  the  actual  death  of  the  vine  or  at  least  in  excessive  weakness  from 
which  it  recovers  with  difficulty. 


2  UNIVERSITY   OF    CALIFORNIA EXPERIMENT    STATION 

One  year  of  the  kind  of  pruning  shown  in  figure  1  might,  with  a 
vigorous  vine,  give  25  per  cent  or  even  50  per  cent  more  than  a  normal 
crop,  but  the  grapes  would  be  of  inferior  quality  and  the  next  year's 
crop  so  much  below  normal  that  there  would  be  a  net  loss.  If  con- 
tinued, the  vines  would  be  permanently  weakened  or  killed. 

The  vine  shown  in  figure  2  had  been  pruned  the  previous  year  to 
one  cane  of  moderate  length  and  two  renewal  spurs.  It  made  an 
extremely  healthy  and  vigorous  growth. 


Fig.  1. — A  Zinf  andel  ' '  pruned  for  crop. ' '     A  short  life  and  a  merry  one. 

When  the  photograph  was  taken  the  vine  was  well  prepared  to  give 
a  very  large  crop  of  good  grapes  the  following  year.  Leaving  three 
or  four  fruit  canes  of  three  to  five  feet  and  four  or  five  renewal  spurs 
of  one  to  two  buds  would  have  enabled  it  to  do  this  and  also  to  produce 
a  growth  of  good  canes  for  the  next  crop. 

Instead  of  this,  the  method  of  pruning  adopted  was  to  leave  all  the 
canes,  thirteen,  and  to  leave  them  of  full  length,  together  with  their 
laterals.  This 'left  approximately  eighty  feet  of  cane  instead  of  the 
fifteen  feet  which  would  have  been  sufficient. 

The  results  in  growth  are  shown  in  figure  3. 

During  the  third  year  the  vine  shown  in  figure  3  made  about  eighty 
feet  of  excellent  fruiting  canes.  This  year,  the  fourth  year,  it  has 
made  hardly  a  single  foot.  What  growth  it  has  made  consists  prin- 
cipally of  slender  twigs  from  five  inches  to  fifteen  inches  long,  half- 
ripened,  and  with  poorly  developed  buds.  It  has  made  one  poor  cane 
about  two  feet  long  at  the  extreme  end  and  one  sucker  about  three 
feel  long  from  near  the  ground. 


CIRCULAR  248]         SOME  COMMON  ERRORS  IN  VINE   PRUNING 


Fig.  2. — A  three  year  old  Sultanina  pruned  "for  all  the  traffic  will  bear." 
(1)  End  of  fruit  cane  of  previous  year.     (2,  3)  Eenewal  spurs  of  previous  year. 


Fig.  3. — A  vine  in  tlie  same  vineyard  a  year  later.     "More  than  the  traffic 
would  bear."     (1,  2)  Ends  of  fruit  canes  of  two  years  before. 


4  UNIVERSITY   OF    CALIFORNIA — EXPERIMENT   STATION 

It  probably  produced  a  large  crop  of  inferior  grapes.  With  such 
weak  growth  the  fruit  could  not  have  been  good.  The  prospects  for 
the  coming  crop  are  meager.  All  that  can  be  done  with  such  a  vine 
is  to  cut  it  back  to  the  old  wood  and  grow  a  crop  of  canes  for  the  crop 
of  two  years  hence. 

A  consideration  of  the  three  principles  mentioned  indicates  how 
we  are  to  avoid  both  disastrous  extremes. 

We  must  leave  enough  fruit  buds  on  a  normal  vine  at  the  winter 
pruning  to  enable  it  to  bear  a  good  crop  the  following  year  and  still  have 
surplus  strength  to  produce  enough  vigorous,  mature  buds  for  the  next 
crop.  Whether  we  have  succeeded  will  be  determined  at  the  pruning 
of  the  following  winter.  If  the  vine  has  gained  in  size  and  vigor,  we 
have  not  utilized  its  bearing  capacity  fully  and  the  number  of  fruit 
buds  left  should  be  increased.  If  it  appears  weak  it  has  been  over- 
taxed and  the  number  should  be  decreased. 

In  this  way  the  vigor  of  the  strong  vines  is  utilized  to  obtain  larger 
crops  and  the  weak  vines  fortified  so  that  they  will  give  larger  crops 
the  following  year. 

This  course  of  procedure  applies  not  only  to  vines  but  to  parts  of 
vines,  to  arms  and  spurs.  A  thick,  vigorous  spur  on  a  Muscat  should 
have  three  or  more  buds ;  a  weak  spur,  if  it  is  necessary  to  leave  it  at 
all.  only  one.  A  vigorous  fruit  cane  on  a  Sultanina  should  be  left 
four  or  five  feet  long,  with  twelve  to  twenty  buds,  a  weaker  cane, 
only  two  to  three  feet,  with  half  the  number  of  buds. 

This  principle  carefully  carried  out  will  maintain  the  vigor  of  the 
vines  and  the  regularity  of  the  crop. 

Figure  4a  is  representative  of  a  young  Muscat  vine  or  other  short 
pruned  variety,  or  the  arm  of  an  old  vine.  In  either  case  it  consists 
of  a  vigorous  side  with  two  large  canes  and  a  weak  side  with  two  small 
canes.  In  figure  4c  one  cane  has  been  left  on  each  side  and  both  cut 
to  about  the  same  number  of  buds.  The  result  will  probably  be  that 
the  weak  side  will  produce  several  small  bunches  of  poor  grapes  and 
make  little  or  no  growth,  while  the  strong  side  will  drop  its  blossoms, 
produce  little  or  no  fruit,  and  be  still  more  vigorous  next  year.  In 
figure  4b  the  length  of  the  spur  or  the  number  of  buds  is  in  proportion 
to  the  vigor  of  the  cane.  The  vigorous  cane  has  been  allowed  four 
fruit  buds  and  will  probably  produce  several  large  bunches  of  good 
grapes  and  make  a  moderate  growth  for  next  year.  The  weak  cane 
has  been  cut  back  to  one  bud  and  will  produce  little  or  no  fruit.  Its 
energies  will  therefore  be  expended  on  producing  stronger  and  more 
vigorous  canes.     The  result  at  the  next  pruning  will  be  that  the  two 


Circular  248]         SOME  COMMON  ERRORS  IN  VINE  PRUNING  5 

sides  of  the  vine  or  arm  will  be  more  nearly  equal  in  vigor  and  size 
and  equally  capable  of  bearing  an  average  crop. 


hS^r 


Fig.  4. — Differential  pruning. 

Another  principle  which  requires  attention  if  the  vines  are  to  be 
permanently  profitable  is : 

4.  The  amount  and  quality  of  all  growth  depends  on  the  amount 
of  sunshine  it  receives. 

Failure  to  bear  in  mind  this  principle  introduces  serious  difficulties 
in  certain  forms  of  cane  and  cordon  pruning. 

In  a  common  method  of  pruning  the  Sultanina  and  the  Sultana, 
several  fruit  canes  are  taken  from  near  the  ground  and  tied  vertically 


b  UNIVERSITY   OF    CALIFORNIA EXPERIMENT    STATION 

to  the  top  of  a  high  stake.  In  consequence  of  their  position,  the  shoots 
from  the  top  buds  grow  more  vigorously  and  shade  the  shoots  from 
below.  The  next  year  when  it  becomes  necessary  to  supply  new  fruit 
canes,  only  weak  and  inferior  canes  are  to  be  found  below.  If  these 
are  tied  up  the  crop  is  small.    If  the  canes  at  the  top  are  taken  there 


Fig.  5. — A  young  Emperor  vertical  cordon. 

is  nothing  to  tie  them  to.  This  condition  becomes  worse  each  year 
if  the  method  is  continued.  Finally,  it  is  usual  to  leave  the  last  canes 
permanently  to  develop  into  three,  four  or  five  trunks  and  to  leave 
spurs  at  their  tops  where  the  only  good  canes  are  to  be  found.  This 
is  a  definite  abandonment  of  the  cane  system  and  all  that  remains  is 
a  vine  with  multiple  trunks  which  are  difficult  and  expensive  to 
handle,  and  which  requires  head  pruning  with  spurs,  a  method  not 
fruitful  with  these  varieties. 


Circular  248]         SOME  COMMON  ERRORS  IN  VINE  PRUNING  7 

The  trellis  system,  in  which  the  canes  are  tied  horizontally  to  wires, 
avoids  these  troubles  by  exposing  the  head  of  the  vine  to  the  sun,  thus 
insuring  a  perennial  supply  of  vigorous  fruit  canes  at  a  place  where 
they  can  be  used.  A  vine  started  with  the  upright  system  is  with 
difficulty  changed  to  the  trellis  system.  This  system  is  described  in 
Circular  191  of  this  Station. 


Fig.  6. — An  old  Emperor  vertical  cordon. 

In  the  vertical  cordon  system,  commonly  adopted  for  the  Emperor, 
similar  difficulties  ensue.  The  vine  is  given  the  form  of  a  long  upright 
trunk  about  four  and  a  half  feet  high. 

On  this  trunk,  when  the  vine  is  young,  are  developed  spurs  or  arms 
equally  distributed  every  six  to  ten  inches  from  the  top  to  near  the 
ground  (see  fig.  5).  Within  a  year  or  two  the  lower  spurs,  shaded  by 
the  growth  at  the  top  of  the  trunk,  weaken  and  produce  small  and 
inferior  canes.     Finally  nothing  grows  except  at   the  top   and   the 


8  UNIVERSITY   OF    CALIFORNIA — EXPERIMENT    STATION 

cordon  character  of  the  vine  is  lost.  The  growth,  concentrated  at  the 
top,  becomes  very  vigorous,  and  loses  the  ability  to  bear  on  short 
spurs  which  is  one  of  the  advantages  of  the  cordon  (see  fig.  6). 

The  horizontal  cordon  system,  in  which  the  trunk  of  the  vine  is 
carried  horizontally  at  about  thirty-six  inches  from  the  ground  to  the 
next  vine,  intensifies  the  cordon  effects  by  making  the  trunks  twice 
as  long  as  in  the  vertical  form  and  makes  it  permanent  by  insuring 
a  continuous  growth  on  all  parts  of  the  trunk,  which  is  equally  exposed 
to  the  sun  along  its  whole  length.  This  system  is  described  in  Circular 
229  of  this  Station. 

The  errors  discussed  are : 

1.  Failure  to  modify  the  pruning  according  to  the  strength  of  the 
vine  or  of  the  cane.  This  results  in  irregular  crops  and  irregular  vines 
and  a  serious  decrease  in  quality  and  average  crop. 

2.  Serious  injury  to  the  vine  or  its  destruction  by  attempting  to 
obtain  excessive  crops  without  regard  to  the  annual  growth. 

3.  Adopting  systems  which"  in  their  nature  cannot  be  permanent, 
i.e.,  vertical  canes  and  vertical  cordons. 

These  errors  are  discussed  more  fully  and  methods  of  avoiding 
them  explained  in  other  publications  which  can  be  obtained  by  appli- 
cation to  the  College  of  Agriculture,  Berkeley,  California. 

The  following  supplementary  references  may  be  found  useful : 

1.  Vine  Pruning  in  California,  Bulletin  241-246.  (Amount  of 
pruning,  pp.  29-31 ;  vertical  canes,  pp.  93-95 ;  vertical  cordons,  pp. 
95-97.) 

2.  Pruning  the  Seedless  Grapes,  Circular  191.  (Methods  of  cane 
pruning. ) 

3.  Cordon  Pruning,  Circular  229.  (Horizontal  unilateral  vine 
cordons.) 

4.  Vine  Pruning  Systems,  Circular  245.  (Types  of  pruning  recom- 
mended for  California.) 


